The present invention relates, first, to a purified, easily produced poly-xcex2-1xe2x86x924-N-acetylglucosamine (p-GlcNAc) polysaccharide species. The p-GlcNAc of the invention is a polymer of high molecular weight whose constituent monosaccharide sugars are attached in a xcex2-1xe2x86x924 conformation, and which is free of proteins, and substantially free of single amino acids, and other organic and inorganic contaminants. In addition, derivatives and reformulations of p-GlcNAc are described. The present invention further relates to methods for the purification of the p-GlcNAc of the invention from microalgae, preferably diatom, starting sources. Still further, the invention relates to methods for the derivatization and reformulation of the p-GlcNAc. Additionally, the present invention relates to the uses of pure p-GlcNAc, its derivatives, and/or its reformulations.
There exists today an extensive literature on the properties, activities, and uses of polysaccharides that consist, in part, of p-GlcNAc. A class of such materials has been generically referred to as xe2x80x9cchitinxe2x80x9d, while deacetylated chitin derivatives have been referred to as xe2x80x9cchitosanxe2x80x9d. When these terms were first used, around 1823, it was believed that chitin and chitosan always occurred in nature as distinct, well-defined, unique, and invariant chemical species, with chitin being fully acetylated and chitosan being fully deacetylated compositions. It was approximately a century later, however, before it was discovered that the terms xe2x80x9cchitinxe2x80x9d and xe2x80x9cchitosanxe2x80x9d are, in fact, very ambiguous. Rather than referring to well-defined compounds, these terms actually refer to a family of compounds that exhibit widely differing physical and chemical properties. These differences are due to the products"" varying molecular weights, varying degrees of acetylation, and the presence of contaminants such as covalently bound, species-specific proteins, single amino acid and inorganic contaminants. Even today, the terms xe2x80x9cchitinxe2x80x9d and xe2x80x9cchitosanxe2x80x9d are used ambiguously, and actually refer to poorly defined mixtures of many different compounds.
For example, the properties of xe2x80x9cchitinsxe2x80x9d isolated from conventional sources such as crustacean outer shells and fungal mycelial mats are unpredictably variable. Such variations are due not only to species differences but are also due to varying environmental and seasonal effects that determine some of the biochemical characteristics of the xe2x80x9cchitinxe2x80x9d-producing species. In fact, the unpredictable variability of raw material is largely responsible for the slow growth of chitin-based industries.
No reports exist today in the scientific literature describing the isolation and production, from material sources, of pure, fully acetylated p-GlcNAc, i.e., a product or products uncontaminated by organic or inorganic impurities. While McLachlan et al. (McLachlan, A. G. et al., 1965, Can. J. Botany 43:707-713) reported the isolation of chitin, subsequent studies have shown that the xe2x80x9cpurexe2x80x9d substance obtained, in fact contained proteins and other contaminants.
Deacetylated and partially deacetylated chitin preparations exhibit potentially beneficial chemical properties, such as high reactivity, dense cationic charges, powerful metal chelating capacity, the ability to covalently attach proteins, and solubility in many aqueous solvents. The unpredictable variability of these preparations, as described above, however, severely limits the utility of these heterogenous compounds. For example, the currently available xe2x80x9cchitinsxe2x80x9d and xe2x80x9cchitosansxe2x80x9d give rise to irreproducible data and to unacceptably wide variations in experimental results. Additionally, the available preparations are not sufficiently homogenous or pure, and the preparation constituents are not sufficiently reproducible for these preparations to be acceptable for use in applications, especially in medical ones. Thus, although extremely desirable, true, purified preparations of chitin and chitosan, whose properties are highly reproducible and which are easily manufactured, do not currently exist.
The present invention relates, first, to an isolated, easily produced, pure p-GlcNAc species. The p-GlcNAc of the invention is a polymer of high molecular weight whose constituent monosaccharides are attached in a xcex2-1xe2x86x924 conformation, and which is free of proteins, substantially free of other organic contaminants, and substantially free of inorganic contaminants.
The importance of the present invention resides in the fact that the problem of unpredictable raw material variability has been overcome. It is, for the first time, possible to produce, by simple means, and on a commercial scale, biomedically pure, p-GlcNAc of high molecular weight and consistent properties. The material produced in the present invention is highly crystalline and is produced from carefully controlled, aseptic cultures of one of a number of marine microalgae, preferably diatoms, which have been grown in a defined medium.
The present invention further describes derivatives and reformulations of p-GlcNAc as well as methods for the production of such derivatives and reformulations. Such derivatizations may include, but are not limited to polyglucosamine and its derivatives, and such reformulations may include, but are not limited to membranes, filaments, non-woven textiles, sponges, gels and three-dimensional matrices. Still further, the present invention relates to methods for the purification of the p-GlcNAc of the invention from microalgae, preferably diatom, sources.
Additionally, the present invention relates to the uses of the purified p-GlcNAc, its derivatives, and/or its reformulations. Among these uses are novel commercial applications relating to such industries as the biomedical, pharmaceutical, cosmetic and agricultural industries, all of which require starting materials of the highest degree of purity. For example, the p-GlcNAc materials of the invention may be formulated to exhibit controllable biodegradation properties, and, further, may be used as part of slow drug delivery systems, as cell,encapsulation systems, and as treatments for the prevention of post-surgical adhesions; and for the induction of hemostasis. For example, the p-GlcNAc materials of the invention exhibit properties that make them ideally suited for a large number of biomedical applications. Some of these properties include but are not limited to: high purity and composition consistency; biocompatibility; controllable biodegradability; and, an ability to immobilize and encapsulate agents, such as therapeutic agents, and cells. These properties are useful, for example, in the formulation of biodegradable barrier devices, improved drug formulations and cell based therapeutics.
The biodegradable barriers of the invention include p-GlcNAc based materials used as devices, for example, as temporary barriers which become resorbed by the body. This category of products include, but is not limited to, devices that prevent the formation of surgical adhesions, stop bleeding, and promote wound healing. Such biodegradable barriers can further be used as surgical space fillers, peridontal barriers or for soft tissue augmentation.
Improved drug formulations of the invention include p-GlcNAc based materials designed to deliver drugs. These new drug formulations are an improvement over traditional drug formulations, in that the drug formulations of the invention provide, for example, increased effectiveness, reduced toxicity and improved bioavailability. These improved drug formulations can be used in combination with many therapeutic agents including, but not limited to, chemotherapeutic agents, such as antitumor agents, as well as antibiotics, antibacterials, antifungals and anti-inflammatory drugs.
Additionally, the present invention relates to cell based therapeutics using p-GlcNAc based materials as a matrix for the encapsulation of cells. For example, p-GlcNAc/cell encapsulations may be used for the implantation of insulin-producing cells in the treatment of diabetes or dopamine-producing cells for the treatment of Parkinson""s disease. The p-GlcNAc cell encapsulations of the invention can also be used for the delivery of cells to regenerate tissue such as, for example, skin, cartilage and bone.